RESUMEN
BACKGROUND:As a leading technique in the treatment of primary stenosis by posterior spinal endoscopy through unilateral approach and bilateral decompression using single channel endoscopy,the long-term efficacy needs to be further observed.There are few reports on the scope of intraoperative resection and few relevant studies on biomechanics and finite element analysis. OBJECTIVE:A three-dimensional finite element model was established to evaluate the effects of bilateral lumbar canal decompression under a one-hole split endoscope on lumbar range of motion and intradiscal pressure,to provide suggestions for clinical operation and theoretical basis for further clinical research. METHODS:A complete L3-L5 vertebral body model was reconstructed by CT images of nine healthy volunteers,which was used as the preoperative model M1.The simulated surgical resection range of L4-L5 was performed,and 1/4,1/3 and 1/2 of bilateral facet joints were removed respectively to obtain models M2,M3 and M4.The range of motion and the maximum Von Mises stress of the four models were compared in the six directions of forward bending,backward extension,left and right bending,and left and right rotation. RESULTS AND CONCLUSION:(1)The L3-L5 finite element model established in this study was effective,and the range of motion was within the range of previous solid studies under six motion states.(2)Compared with the M1 model,the L4-L5 lumbar spine range of motion increased with the increase of resection range in M2 with M3 and M4 models under forward bending,left and right bending and left and right rotation loading,and the difference was significant(P＜0.05).Under posterior extension loading,there was no significant difference in lumbar range of motion between M1 and M2(P＞0.05),but there was a significant difference of M1,M3 and M4(P＜0.05).(3)The range of motion of the L3-L4 lumbar spine had no significant change with the increase of bilateral facet arthrotomy(P＞0.05).(4)There was a significant difference in the maximum value of L4-L5 Von Mises between M1 and M2(P＜0.05),and there was a significant difference in the maximum value of L4-L5 Von Mises between M1 and M3,M4(P＜0.01),and the maximum value of L4-L5 lumbar von Mises increased with the increasing range of bilateral facet joint resection.Resection of more than 1/3 was particularly obvious.(5)The maximum value of Von Mises in the L3-L4 lumbar spine was increased with the increase of the resection range under forward bending,left and right bending and left and right rotation loading and the difference was significant(P＜0.05).(6)The results exhibited that the L4-L5 lumbar motion and intervertebral disc pressure increased with the increase of the excision range.Intervertebral disc pressure at L3-L4 increased with the increased extent of excision,but the lumbar range of motion was not significantly affected.In conclusion,the stability of the operative segment may be affected by the increase in the scope of facet joint resection.Although the immediate stability of adjacent segments is not affected,it may accelerate disc degeneration.
RESUMEN
Objective To investigate changes in the intraocular pressure(IOP) and anterior chamber angle in patients with chronic renal failure before and after hemodialysis. Methods Fifty?eight patients(116 eyes) with chronic renal failure were measured with Goldmann applanation tonometer and anterior segment optical coherence tomograph. The patients were divided into three groups based on gonioscopy results:the narrow angle group(22 eyes),the Iris neovascular group(3 eyes)and the open angle group(91 eyes). IOP was measured by Goldmann applanation tonometer in patients in the three groups before and after hemodialysis. Anterior chamber angle opening distance (AOD) was detected by anterior segment optical coherence tomograph before and after hemodialysis. The blood urea nitrogen,creatinine,albumin were also determined before and after hemodialysis. All changes in the parameters were analyzed with a paired t test. Results The IOP in narrow angle eyes and in neovascular eyes increased significantly after hemodialysis ,while the IOP in open angle eyes showed no significant changes. The AOD decreased significantly after hemodialysis. The blood urea nitrogen and creatinine decreased significantly in 58 patients,while albumin increased after hemodialysis. Conclusion The IOP in narrow angle eyes and in neovascular eyes increased after hemodialysis ,correlating with the resistance increase of aqueous outflow pathway and the change of plasma osmotic pressure. As a result ,it is recommended that the condition of eye of patients with chronic renal failure should be checked ,and patients should receive appropriate controlling measure or treatment before hemodialysis.